Damper control for unit heaters



mospheric. 'sides of a diaphragm supply ample force for acreissued Oct. 14, 1941 DADIPEB.' CONTROL UNIT HEATEBS nal-aia c. ramener, winners, n1., assignmto The Powers Regulator Company, Chicago, Ill., a corporation o! Illinois Original No. 2,213,092, dated August 27, 1940, Serial No. 294,267, September 1l, 1939. Application for reissue May 28, 1941, Serial No.

'l' Claims.

My invention relates to heating appliances ,nd particularly to a unit heater and ventilator raving novel means for controlling-the fresh air ntake damper commonly used therewith.A

In the operation of heating appliances it has ieen the practice for many years to provide neans acting to close the fresh air inlet when- `:ver the operation ofthe circulating'fan is inprrupted. This has commonlyv been accomfalished by providing an electro-pneumatic valve, fn series with the fan motor, rthe valve having ghe function of venting the dampermotor whenver the current to the fan motor is interrupted. An arrangement of this character involves nsiderable wiring and other complications. nd it is the object of this invention to provide eans for accomplishing the desired result v Qwithout the use of electrical connections.

In order to interrupt the supply oi' air from ythe thermostat to the damper motor and to vent the motor, I provide a simple positively acting valve operable by either the separate or combined effects of static and velocity pressure. When the fan is in operation the pressure within the unit heater casing is slightly below atimospheric, while the. velocity pressure, made efffective through alPitot tube, is slightly above at- These forces acting on opposite tuating a valve that serves to accomplish the d purpose. s The invention will be more readily understood by reference to the accompanying drawing, in which,

Fig. l is a sectional view through a unit heater arranged in accordance'with my invention; and,

Fig. 2 is an enlarged sectional view through a valve arrangement such as contemplated.

In the drawing I have indicated 4a unit heater casing III having a fresh air inlet opening and a heated air outlet I2. Within the casing I provide aheat exchange element Il, the supply oi heat to which is controlled by a uid pressure motor valve Il. A pair of blower fans l5 are operated by an electric motor I6, an operating (C1. zas-ss) is permitted to pas said valve 22 is carried through pipe 23 to a damper motor 24 so arranged that a damper 25 controlling the fresh air inlet is held in open position by the pressure admitted through said Apipe 23. Spring means 26 serveztolclose said damper. p

Associated with said valve 23 is a diaphragm 21 held within a casing 28. The upper side of the'diaphragm 21 is open to the space within the unit heater through the opening 28 in the casing. 'lhe lower side of the diaphragm is in communication with a Pitot tube. 30 located in the air-stream from one of the lans l5 through a A' stem 32 connected to the diaphragm 21 is engaged by a light. ilexible vspring 33 and contacts a button 34 forming a part of the valve 22. This button is carried'on a diaphragm 35, the button having an exhaust passage I6 controlled by a valve 31.. A light coiled spring 38 tends to unseat the valve 31. Mounted in thevalve body 22 is a second valve 39 seated by a spring lll that is strongerthan the spring 38, this valve controlling the passage of air from the pipe 2| to the pipe 23 through the appropriate passages. A pin 1| provides a thrust connection between valves 31 and 39.

In practice, the fan motors being in operation,

a vstatic pressure somewhat less than ,-atmosdamper motor 24 to maintain the damper in open switch Il for which may be provided at a remote point. A thermostat Il of common form through pipe 2B to the valve Il,v a branch pipe f 2| conveying the air under pressure to the threeway valve 22, best shown in Fig. V2. The air lthat position. Upon interruption of the fan motor the static pressure within the heater casing will' return to normal and the velocity pressure theretofore exerted on the lower side of the diaf the use of electrical apparatus of any kind.

While I have shown means providing for operation of the diaphragm by the' combined effect of the static and velocity pressures, it is possible that the result might be secured by the use oi' either of said pressures andthe invention should be so considered.

I claim:

l. In a unit heater having a casing and a fresh air intake damper and motor, the combination of thermostatically controlled air-pressure-means acting on said motor for maintaining said damper in open position, a blower for circulating air through said casing, a three-way valve ior alternately admitting said air under pressure to said motor and exhausting said air to permit said damper to close, and means for operating said three-way valve, said means including a diaphragm, and a Pitot tube located in the air stream from said blower. one side of said diaphragm being aiected by the static pressure in said casing and the other side by the pressure developed by i said Pitot tube.

,stream from said blower, one side of said diaphragm being -affected by the minus static pressure in said casing and the'other lside by the plus pressure developed by said Pitot tube.

3. In a unit heater. the combination of a casing having an outlet and a fresh air inlet, a damper for controlling said inlet, a motor for controlling said damper. a thermostat for controlling air press e acting on said damper motor and so arrang that pressure is necessary to maintain said damper in open position, a. fan for causing.

the movement of air through said casing, a threeway valve for alternately admitting said air under pressure to said motor and exhausting said air to permit said damper to close, and means for operating said three-way valve, said means including a diaphragmand a. Pitot tube located in the air stream from said blower and connected to one side of said diaphragm. said diaphragm being affected by the pressure developed by saidt Pitot tube.

4. In a unit heater. the combination of a casing having an outlet and a fresh air inlet,a damper for controlling said inlet, a moto'r for controlling said damper. a thermostat for controlling air pressure acting on said damper motor and so ar-i ranged that pressure is necessary to maintain said damper in open position, a ian for causing the movement of air through said casing, a threeder pressure to said motor and exhausting said air to permitv said damper to close, and means for operating said three-way valve, said means including a diaphragm and a. Pitot tube located in the air stream from said blower, connected to one side 0i said diaphragm, one side of Said diaphragm being ailected by the pressure developed by said Pitot tube, and the other side being affected by the minus static pressure in said casing.

5. In a unit heater having a casing and a fresh airl intake damper and motor, the combination of thermostatically controlled air-pressure-means acting on said motor for maintaining said damper in openr position, .a blower for circulating air through said casing, a three-way valve for'alternately admitting said -air under pressure to said motor and exhausting said air to permit said damper to close. and means for operating said three-way valve, said means including a diaphragm, subject to the pressure within the casing, one side of said diaphragm being affected by the static pressure in the casing. the pressure in said casing being below atmospheric during the operation of said blower and being restored to atmospheric with consequent change in the pressure effective on said diaphragm when the operation oi the blower is interrupted.

6. In a unit heater'having a casing and a fresh air intake damper. 'and motor, the combination of thermostatically controlled air-pressure-means acting on said motor for maintaining said damper in open position, a blower for circulating air through said casing, a three-way valve for alternately admitting said air under pressure to said motor and exhausting said air to permit said damper to close, and means for operating said three-way valve, said means including a diaphragm, within the casing, one side or said diaphragm being affected by the static pressure in said casing-being below atmospheric during the operation ot said blower and being restored to atmospheric with consequent change in the pressure eii'ective on said diaphragm when the operation ofthe blower is interrupted.

'7. In a heating device having a casing and a fresh air intake damper and motor, the combination of air-pressure-means acting on said motor for maintaining said damper in one position, a blower for circulating air through said casing, a three-way valve for alternately admitting said air underpressure to said motor and exhausting said air to change the position of said damper. and means for operating said threeway valve, said means including a. diaphragm, the position of said diaphragm being controlled by air pressure conditions developed by said blower,

v whereby during operations oi' the blower the three-way valve ispositioned to maintain said way valve for alternately admitting said air undamper in open position and positioned to effect closing of the damper when the blower is idle. HARALD MUELLER.

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